Technical Field
This invention relates to a transparent solar heat absorbing apparatus that utilizes solar energy while allowing sunlight to pass through the apparatus, a solar water-heating system equipped with the transparent solar heat absorbing apparatus, and a solar cogeneration system equipped with the transparent solar heat absorbing apparatus.
Description of Related Art
Conventionally, a solar cell (photoelectric converter) that converts sunlight to electrical energy and a solar heat absorbing apparatus that converts sunlight into thermal energy have been known to utilize solar energy.
The solar cell converts sunlight into electrical energy (i.e., generate power) by absorbing the sunlight in a specific wavelength range. An amorphous silicon (a-Si) solar cell absorbs the sunlight in the wavelength range between about 300 nm and 700 nm, a cadmium tellurium (CdTe) solar cell absorbs the sunlight in the wavelength range between about 300 nm to 850 nm, and a copper indium gallium selenide (CIGS) solar cell absorbs the sunlight in the wavelength range between about 300 nm to 1000 nm. That is to say, solar cells can convert the sunlight into the electrical energy only in the wavelength range between about 300 to 1000 nm. In other words, the solar cells cannot effectively utilize the sunlight (solar energy) in the wavelength range between 1000 to 2500 nm (i.e., near infrared light). Hence, the energy conversion efficiency of the solar cell (photoelectric converter) is not sufficiently high. Note that a single crystal silicon (single crystal-Si) solar cell can convert the sunlight in the wavelength range greater than 1000 nm but is expensive and difficult to increase the size.
For the near infrared light (in the wavelength range approximately between 700 and 2500 nm), it is generally more effective to convert it into the thermal energy rather than into the electrical energy. Therefore, it is common to use a solar heat absorbing apparatus to convert the near infrared light (solar energy thereof) into the thermal energy. As is known, a solar water heating device can convert the near infrared light of the sunlight (solar energy thereof) into the thermal energy and generate heated water with the converted thermal energy, for example. However, since the color of the solar water heating device (solar heat absorbing apparatus) is commonly black, it is not preferable to install the solar water heating device on a certain place, such as a transparent roof of a balcony used for daylighting and for rain cover and a balcony with a glass handrail or with a glass fence. Hence, the installation places of the device are limited. Further, when a photoelectric converter (solar cell) is provided next to the solar water-heating device (solar heat absorbing apparatus) to obtain more energy from the sunlight, both the solar water-heating device and the photoelectric converter require installation places respectively, resulting in an increase of the installation space.
To overcome the drawbacks, a solar system has been taught by Japanese Laid-Open Patent Application No. 2006-078007. In this solar system, a solar water hearting device (solar heat absorbing apparatus) allows a part of the sunlight to pass through the device and is installed on top of a photoelectric converter (solar cell). Further, the solar water-heating device and the photoelectric converter are integrally supported by an outer frame. Specifically, the solar water-heating device includes a water tank, and the bottom and top parts of the water tank are formed of transparent materials. Further, the inside of the water tank is divided into a plurality of areas by a plurality of partition panels. In the solar water-heating device, the water in the tank absorbs thermal energy of the sunlight (mainly, the near infrared light thereof) to heat the water with the absorbed thermal energy as the sunlight passes through the water in the tank. This conventional solar system can also generate power with the photoelectric converter by using the sunlight having passed through the solar water-heating device while heating the water by using the solar water-heating device. As a result, the conventional solar system can utilize wider wavelength ranges of the sunlight to obtain energy compared to the system equipped only with a solar water-heating device or a photoelectric converter. In other words, the conventional solar system can improve the conversion efficiency of the solar energy. Further, since the solar water-heating device of the conventional solar system allows the part of the sunlight to pass through, the solar water-heating device can be disposed on top of the photoelectric converter. With this, it can prevent an increase of the installation space.